Summary of Work: Mucin hypersecretion is a feature common to a variety of airway diseases associated with airway inflammation. Airway epithelial cells respond to a variety of pro-inflammatory cytokines with an increase in mucin secretion. Human airway epithelial cells express products of at least 7 mucin genes. Ribonuclease protection assays have been developed for the quantitation of steady-state mRNA levels of mucin gene transcripts in airway epithelial cells in culture. Analysis of changes in steady-state mRNA levels of at least 4 of these genes in response to proinflammatory mediators and to changes in intracellular second messengers is in progress.